Wound dressing

ABSTRACT

A wound dressing includes an absorbent core having opposed proximal and distal surfaces including central and border portions, a discrete skin adherent, elastomeric gel facing layer having a distal surface secured to the proximal surface of the absorbent core and a plurality of through extending apertures arranged in a pattern. A pressure sensitive adhesive layer is applied to the facing layer on at least a segment of a proximal surface opposed to the distal surface thereof. The adhesive layer has greater skin adherence properties than the elastomeric gel of the facing layer.

[0001] This application claims the benefit of U.S. ProvisionalApplication Nos. 60/437,146 filed 31 Dec. 2002, 60/482,775 filed 27 Jun.2003, 60/503,546 filed 17 Sep. 2003, and 60/518,317 filed 10 Nov. 2003.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a wound dressing, and moreparticularly to a wound dressing having a construction with improvedskin adherence and absorptive capabilities, and methods for producingthe same.

[0004] 2. Discussion of Related Art

[0005] Historically, many diverse materials of various origins have beenused to treat wounds by absorbing wound fluids and tissue, hereinaftergenerally referred to as exudate, from a wound site with some type ofabsorbent material. In recent years, use of polymeric-based wound careproducts have become increasingly popular to control wound siteenvironmental factors such as water vapor, oxygen permeability,bacterial impermeability, and absorption of exudate. Such wound careproducts are tailored to meet specific requirements includingconformability to a body portion, selective adherence to a wound bed,and adhesiveness to the skin surrounding the wound site.

[0006] Recently, occlusive or moisture-retentive dressings have gainedincreasing acceptance in treating wounds, in particular pressure soresand ulcers. A wide variety of types of structures are known in the artfor use in or as occlusive dressings and generally comprise componentsfor receiving, absorbing and retaining exudate. Typically, these woundcare products include polymeric foams, polymeric films, particulate andfibrous polymers, hydrogels and hydrocolloids. Dressings with at leastone of these components promote wound healing by providing a moistenvironment, while removing excess exudate and toxic components, andfurther serve as a barrier to protect the wound from secondary bacterialinfection. While these known occlusive wound dressings can effectivelymanage a wound, many have been found to possess certain limitations ordisadvantages.

[0007] In wound care, one of the main objectives of a wound dressing isto increase, improve or maximize utilization of the absorbent capacityof the dressing so as reduce or eliminate maceration, and facilitate thehealing process of the wound. The control of exudate is of primeimportance if a moist wound microenvironment is to be maintained.Unfortunately, many wound dressings have been found to remove all theexudate that a wound produces, thereby causing a “dry” wound that isundesirable in the wound healing process or in the alternative, suchwound dressings have been found to absorb or control the exudateinsufficiently, thereby leading to a pooling of the exudate which mayincrease the risk of bacterial proliferation and lead to infection.

[0008] Many wound dressings in the prior art include an absorbent layerhaving absorptive capabilities. Typically, the absorbent layer containshydrophilic materials that absorb exudate and permit the wound dressingto be left in place for a period of days. Such absorbent layers maycomprise a non-woven material or foam containing hydrocolloid particlessuch as the dressings described in U.S. Pat. Nos. 4,373,519 and6,566,576, or a hydrophilic foam layer, such as in the dressingsdescribed in U.S. Pat. Nos. 5,409,472, 5,782,787, 6,040,492, 6,051,747,and 6,486,378.

[0009] While absorbent layer dressings are configured to absorb woundexudate, they often possess the disadvantage of being limited in theamount of exudate that may be absorbed. The limit to the maximumabsorption of absorbent foam is often directly related to theirgeometrical size prior to absorbing a fluid. For example, hydrophilicfoams may expand only to 12-15% of their original size. Anotherdisadvantage is that it has been found that a certain amount of theexudate can be “squeezed” out of absorbent foam dressings due to poorliquid retention. The ability of exudates to be squeezed from the foamlayer, and thus dressing itself, poses a risk of infection and mayinterfere with the healing of the wound.

[0010] Yet another disadvantage with known dressings is that absorptionof exudate by an absorptive layer in contact with the wound causes thecentral portion of the applied dressing to swell and push up against thewound. Continued swelling can induce separation of the skin adherentlayer from the skin outside the wound area, especially at the border ofthe wound dressing whereat a “curling” effect may occur. This excessiveswelling of the wound dressing may further lead to leakage of theexudate from the periphery of the dressing, thereby providing a tractfor the invasion of pathogenic microorganisms and further promotingmaceration of the wound site.

[0011] Conventionally, a backing layer is provided that comprises aliquid impervious film that is attached to the absorbent layer toprevent exudate from seeping from the dressing. A difficulty arisesduring fluid uptake in that as the absorbent core expands, the backinglayer must accommodate the expansion of the absorbent layer withoutcausing curling of the dressing. An attempted solution to this problemis described in U.S. Pat. No. 4,738,257 which discloses a backing layerformed of a thin elastic sheet which is yieldable as the absorbent coreswells. It has been found, however, that a liquid impervious plasticfilm cannot be made to sufficiently stretch in keeping with theexpansion of the absorbent layer, and as a result, the filmcounteracting with the swelling absorbent layer may produce theaforesaid curling at the border of the dressing. Another proposedsolution is provided in U.S. Pat. No. 6,040,492 which discloses a wounddressing that includes a backing layer that is attached to an absorbentfoam core and includes a plurality of wrinkles that substantiallyflatten as the foam core swells. While the backing layer may accommodatethe expansion of the foam core, the fluid uptake of this wound dressingis limited by the expandability of the foam core itself. Accordingly,due to the limited absorptive capacity of the foam core, the dressingmust be replaced often.

[0012] Ideally, a wound dressing must be adhesive in nature such that itmay attach to the wound site while being non-toxic and eliciting no morethan a minimal allergenic response. Moreover, a wound dressing shouldpossess the ability to prevent bacteria from entering the wound from theambient environment while providing a suitable moisture transmissionrate.

[0013] It has been found, however, that many known occlusive dressingspossess the disadvantage of relying solely on a pressure sensitiveadhesive layer that is used to secure the dressing to skin, for instancean acrylate glue having a high specific adhesiveness. Typically, a wounddressing with only an adhesive has a tendency to strip the centralportion of the dressing from the wound when removed from the wound andthus may damage healing tissue.

[0014] Wound dressing have been commercially available that include anabsorbent foam core with a wound contacting surface coated with a layerof silicone gel. The silicone gel randomly lines portions of the wallsof the pores of the absorbent foam to form a plurality of randomlyformed apertures. These apertures are formed by capillary action when anuncured silicone gel is applied to the foam core. One drawback to thisapproach is that the silicone gel may close some of the pores, andanother drawback is that the holes are randomly formed which may lead tolocalized areas that inhibit the uptake of the exudate into the foamcore. While in some applications it may be desirable to provide thewound dressing with a greater concentration of apertures at selectedregions of the wound dressing to increase exudate uptake at such areas,this approach does not accommodate such a formation of a predeterminedpattern of apertures. Furthermore, another drawback to this approach isthat the surface roughness of the silicone layer is largely dependentupon the surface of the foam to be coated, and in the event it isdesired to obtain a smooth silicone layer to be worn on the skin, thisapproach fails to yield such a smooth silicone layer.

[0015] Developments in the field of silicone manufacturing have ledOssur hf of Reykjavik, Iceland, and assignee of the present invention,to produce silicone products adapted for skin contact that providesuperb softness, gentle skin contact, and may include unique skin careingredients. In particular, such silicone manufacturing has led toadvances in improved comfort and cushioning of prosthetic suspensionliners that have excellent durability and intimacy using proprietarysilicone technology of Ossur hf. It has been found that by applying thesilicone technology of Ossur hf to produce an ultra-thin, perforatedtacky silicone sheet, a silicone adhesive layer can be produced thatpossesses superior gentle adherence to wound sites while not damagingskin and the wound bed due to single or repeated removal of the siliconelayer.

[0016] Despite the availability of a variety of absorbent wounddressings, there is a need and a demand for an improved wound dressingwhich prevents wound trauma upon wound dressing changes, improves thedurability and lifetime of the wound dressing, anatomically conforms toa wound and possesses improved fluid uptake, retention and removalproperties. Most importantly, it is desired to produce a wound dressinghaving an adhesive layer that does not possess the drawbacks of knownadhesive layers, and instead, gently adheres and detaches from a woundsite while providing superior fluid uptake. Moreover, there is a needand a demand for an improved method of forming such an improved wounddressing that is both simple and cost effective.

SUMMARY OF THE INVENTION

[0017] The present invention is directed to an improved wound dressingpossessing superior skin adherence capabilities. In an embodiment of theinvention, a wound dressing includes an absorbent core having opposedproximal and distal surfaces including central and border portions, adiscrete skin adherent, elastomeric gel facing layer having a distalsurface secured to the proximal surface of the absorbent core and aplurality of through extending apertures arranged in a pattern. Apressure sensitive adhesive layer is applied to the facing layer on atleast a segment of a proximal surface opposed to the distal surfacethereof. The adhesive layer has greater skin adherence properties thanthe elastomeric gel of the facing layer.

[0018] In another embodiment of the invention, the adhesive layer islocated along at least one segment of a border portion of the facinglayer corresponding to the border portion of the absorbent core, and theapertures of the facing layer are only located in the central portion ofthe facing layer.

[0019] In yet another embodiment of the invention, the wound dressingconsists of a discrete skin adherent, elastomeric gel facing layerhaving a distal and proximal surfaces and a plurality of throughextending apertures arranged in a pattern, and a pressure sensitiveadhesive layer applied to the facing layer on at least a segment of aproximal surface thereof. The adhesive layer has greater skin adherenceproperties than the elastomeric gel of the facing layer.

[0020] Numerous other advantages and features of the present inventionwill become more readily apparent from the following detaileddescription of the invention, the accompanying examples, drawings andthe appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021]FIG. 1 is a perspective view of an embodiment of a wound dressingof the invention;

[0022]FIG. 2 is a sectional view of the wound dressing along line II-IIin FIG. 1;

[0023]FIG. 3 is a perspective view of an embodiment of a wound dressingof the invention;

[0024]FIG. 4 is a plan view showing an embodiment of a facing layer ofthe invention;

[0025]FIG. 5 is an enlarged view of a section of another embodiment ofthe wound dressing in FIG. 2;

[0026] FIGS. 6-8 are sectional views illustrating progressive swellingof the wound dressing in FIGS. 1-2 over a wound site;

[0027]FIG. 9 is an enlarged view of a section of the wound dressing inFIG. 8;

[0028]FIG. 10 is a plan view showing an embodiment of a facing layer ofthe invention;

[0029]FIG. 11 is a plan view showing an embodiment of receptacles of anabsorbent core of the invention;

[0030]FIG. 12 is a plan view showing an embodiment of a facing layer ofthe invention;

[0031]FIG. 13 is an elevational view showing another embodiment ofreceptacles and a facing layer of the invention;

[0032] FIGS. 14-16 are plan views showing embodiments of facing layershaving regions with different degrees of skin adherence of theinvention;

[0033] FIGS. 17-18 are elevational views showing embodiments of abacking layer having a skin adherent border section of the invention;

[0034]FIG. 19 is a perspective view of an embodiment of a perforationplate for forming apertures in a facing layer of the invention;

[0035]FIG. 20 is an elevational view showing the perforation plate ofFIG. 19;

[0036] FIGS. 21-23 are schematic views showing arrangements for formingapertures in facing layers of the invention;

[0037]FIG. 24 is a perspective view of an arrangement for formingapertures in the facing layer of the wound dressing of FIG. 23;

[0038] FIGS. 25-26 are schematic views showing an arrangement forforming receptacles in an absorbent core of the invention;

[0039] FIGS. 27-28 are schematic views showing an arrangement fordepositing discrete portions of absorbent material in receptacles of anabsorbent core of the invention;

[0040]FIG. 29 is a cross-sectional view showing an embodiment of aplaten used to apply a backing layer to an absorbent core of theinvention; and

[0041] FIGS. 30-34 are schematic views showing an arrangement forapplying a backing layer to an absorbent core of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0042] As shown in FIGS. 1 and 2, the wound dressing 10 of the presentinvention preferably includes a perforated hydrophobic, skin adherentfacing layer 12, an absorbent core 14, and a liquid impervious, moisturepermeable backing layer 16. The wound dressing depicted in FIG. 1 is ina dry state substantially devoid of moisture. As more fully exemplifiedin FIG. 2, the absorbent core 14 defines a proximal surface p that isintended to face towards a wound surface w and a distal surface d thatis opposed to the proximal surface p and faces away from a woundsurface. In a basic configuration, the dressing 10 comprises the facinglayer 12 secured to the proximal surface p of the absorbent core 14 andthe backing layer 16 attached and sealed to at least part of the distalsurface d of the absorbent core 14.

[0043] In a preferred embodiment, the absorbent core 14 defines aplurality of receptacles 18 arranged in a predetermined pattern whereinthe receptacles 18 are defined as a repeating series of cylindricalcompartments. As shown in FIG. 2, the receptacles 18 open at the distalsurface d of the absorbent core 14 and extend a distance into theabsorbent core 14 a distance t₁, short of its entire thickness t. Thereceptacles may assume a variety of configurations and may becylindrical in shape, extend transversely along at least a portion ofthe distal surface of the absorbent core, or assume other possibleconfigurations as will be discussed below. The plurality of receptacles18 contain discrete portions of absorbent material 20 that absorbexudate from the wound and migrate from the receptacles 18 towards thebacking layer 16 upon absorption of such exudate.

[0044] As illustrated in FIG. 2, the absorbent core 14 generally definescentral, intermediate and border portions 22, 23, 24. Preferably, thebacking layer 16 is secured to the border portion 24 of the absorbentcore 14 and sealed along its periphery. The border portion 24 preferablyincludes a bevel 28 defined near or along a peripheral edge thereof andis provided to retain any loose absorbent material 20 from thereceptacles 18 within the dressing 10. As will be discussed more fullybelow, the backing layer 16 is preferably lightly adhered to the centralportion 22 of the absorbent core 14 when the dressing 10 is in a drystate.

[0045] The backing layer 16 of the dressing 10 preferably includes acompliant element 26 that is interposed between the central and borderportions 22, 24 of the absorbent core 14. The compliant element 26 isgenerally concentric with the central portion 22 and comprises a portionof the backing layer 16 that may not be adhered to the absorbent core 14when the dressing 10 is in a dry state. Preferably, the compliantelement 26 includes at least one concentric ridge. While FIG. 2 showsthe dressing 10 with a compliant element 26 having only one concentricridge 30. FIG. 3 illustrates a dressing 10 having a plurality of ridgeswherein inner and outer ridges 31, 32 extend outwardly from the distalsurface d of the absorbent core 14, and generally constitute inner andouter boundaries of the compliant element 26.

[0046] It will be understood that the compliant element may assume avariety configurations. For example, the orientation of the compliantelement may be arranged in a variety of directions such as the ridgeextending in a range of directions from being generally parallel to theabsorbent core on the border portion side of the compliant element tobeing generally parallel to the absorbent core on the central portionside of the compliant element.

[0047] As shown schematically in FIG. 5, the compliant element 26 is notlimited to being positioned generally along the intermediate portion ofthe absorbent core. The compliant element 26 may be positioned on theborder or the central portions of the wound dressing wherein thecompliant element 26 may include at least one ridge 30 or segmentthereof on at least one of the border or central portions of the wounddressing. Such adaptation of the wound dressing to include a compliantelement on at least one of the border or central portions of the wounddressing may be provided to improve the expandability and distension ofthe backing layer relative to the distal surface of the absorbent core.

[0048] The facing layer 12 is preferably secured to the proximal surfacep of the absorbent core 14. The facing layer 12 includes a plurality ofapertures 34 that are preformed in a pattern prior to securing thefacing layer 12 to the absorbent core 14. As shown schematically inFIGS. 2 and 4, the plurality of apertures 34 may be arranged in apredetermined pattern. The plurality of apertures 34 may be configuredto correspond to regions near or at the plurality of receptacles 18 ofthe absorbent core 14 so as to transport exudate from a wound site tothe absorbent core 14. The facing layer 12 is preferably secured only tothe proximal surface p of the absorbent core 14 and preferably does notcoat the walls of the pores or holes of the absorbent core 14 definednear the proximal surface p thereof. It will be understood, however,that portions of the facing layer may fill irregularities disposed alongthe proximal surface of the absorbent core or pores of the absorbentcore so as to improve the security of the facing layer to the absorbentcore.

[0049] While not wishing to be bound by a particular mechanism ofoperation, the present invention is intended to function as a dressing10 in the manner depicted in FIGS. 6 to 8, after application of thedressing to a fluid-exuding skin wound. It will be understood that inthe context of the invention, the terms fluid, moisture and exudate areused interchangeably regarding wounds and wound dressings. The dressing10 is placed onto a wound site w with the facing layer 12 directed overthe wound bed b. The facing layer 12 may adhere to the intact skinaround the wound site w as well as to the wound bed b. The dressing 10is maintained in close apposition to the wound bed b in part by thecapillary action of the exudate entering the absorbent core 14 and bythe facing layer 12.

[0050] As illustrated in FIG. 6, fluid exuded by the wound bed b will bedrawn through the apertures 34 towards the absorbent core 14, and theabsorbent material 20 contained in the receptacles 18. After beingapplied over the wound site w for an extended period of time, theapplied dressing 10 may appear as shown in FIG. 7 with a slightlyenlarged domed, reservoir configuration 36 extending over the centralportion of the absorbent core 14. The reservoir 36 is caused by theabsorbent material 20 that has absorbed a desired quantity of exudatefrom the receptacles 18 and discrete portions thereof have swelled andmigrated from the receptacles, thereby causing distension of the backinglayer 16. The swollen exudate-laden discrete portions of absorbentmaterial 20 cause the backing layer 16 to detach from the distal surfaced of the absorbent core 14 in a predictable manner and to distendupwardly to further permit continued absorbing and swelling of thedressing 10 over the wound site w. In addition, the absorbent core 14will expand or swell both transversely and longitudinally, and the areaof absorbent core 14 will generally increase with increased fluidabsorption.

[0051] While the backing layer 16 remains sealed along the borderportion of the dressing 10, the reservoir 36 is formed such that it isdefined between the backing layer 16 and the distal surface d of theabsorbent core 14, and sealed along the border portion 24. The reservoir36 permits the migration of the swollen discrete portions of absorbentmaterial 20 from the receptacles 18 and greatly expands the retention offluid from the wound bed b. The compliant element 26 effectivelyfunctions as a flexible joint for the backing layer 16 by permittingadditional expansion of the backing layer 16 in providing additionalflexibility and expansion of the backing layer 16 due to the swelling ofthe absorbent material 20. As shown in FIG. 8, the dressing 10 hasnearly reached its swelling capacity and the backing layer 16 hasdistended to its maximum. Most notably, at this advance stage ofswelling, the border portion 24 of the dressing 10 remains attached tothe wound site w due to the provision of the compliant element 26 whichcompensates for the expansion and swelling of the absorbent core 14 andthe absorbent material 20, and the distension of the backing layer 16.It will be further noted that the ridge 30 generally does not fullyflatten relative to adjacent portions of the backing layer 16 andgenerally extends outwardly, at least in part, from the distal surface dof the absorbent core 14 and in relation to the distended portion of thebacking layer 16 delimited by the compliant element 26.

[0052] It will be understood that the preferred facing layer 12 also hassuitable elastic properties to enable it to stretch as the absorbentcore 14 expands laterally.

[0053] When the dressing 10 has expanded to a maximum capacity, definedas an exudate-laden or fully saturated dressing, it will be desirable toremove and replace the dressing 10. When in a saturated or fullyexudate-laden stage, the corners along the border portion 24 of thedressing 10 generally remain adhered to the wound site w despite theexcessive uptake of exudate, as exemplified in FIG. 9, since the facinglayer 12 provides sufficient adherence to the skin surrounding the woundsite w. By observing the extent of swelling of the dressing in relationto the degree of fluid uptake into the absorbent core and by theabsorbent material, one can be visually determine when it is appropriateto remove the dressing.

[0054] As exemplified in FIG. 10, the dressing 10 may include anadditional adhesive 19 disposed on the facing layer 12. Preferably, theadhesive 19 is deposited on the facing layer 12 at or near a portioncorresponding to the border portion of the absorbent core 14. Thepressure sensitive adhesive 19 is preferably a tacky pressure sensitivesilicone or an acrylate adhesive known in the art of wound dressings.

[0055] In a preferred embodiment, the absorbent core 14 comprisespreferably a hydrophilic synthetic polymer conformable to body surfacesand adapted to be capable of absorbing fluid. It is desirable that theabsorbent core absorb exudate rapidly so as to enhance its effectivenessin the dressing of the invention, and in particular, the fluid uptake tothe receptacles containing the absorbent material. In addition toabsorption, an effective wicking mechanism is desirable, that is theabsorbent core should rapidly direct fluids away from the proximalsurface of the absorbent core to more remote areas for storage (i.e.,the receptacles containing the discrete portions of absorbent material),so as to minimize local saturation and maximize the efficiency of theabsorbent core.

[0056] A preferable absorbent core is constructed of flexible open-cellfoam that is at least slightly hydrophilic. Suitable foams have an opencell size of 30 to 700 microns, and preferably a cell size of 50 to 300microns. The open cells permit transport of fluid and cellular debrisinto and within the foam, and it preferred that the cell size of areasof the foam be of sufficient size to encourage capillary action andpromote fluid transport.

[0057] The absorbent core may expand about 135% of its size whensaturated with fluid. When combined with the facing and backing layer ofthe invention, the absorbent core may expand to only about 110% of itsdry size when exudate laden.

[0058] In accordance with one embodiment of the invention, the absorbentfoam comprises a gradient of cell sizes across the thickness of theabsorbent core such that the cell size decreases in the direction of thedistal surface and of the absorbent core. Since the cell sizes aregreater at and near the proximal surface of the absorbent core, thecapillary forces are stronger and therefore will drain fluid near theproximal surface of the absorbent core and draw the fluid towards thereceptacles. In addition, the absorbent foam may include a cell sizegradient that is directed towards the receptacles, thereby providinglocalized regions in the absorbent foam that are configured to haveincreased capillary forces directed towards the receptacles to aid inthe guidance of fluid thereto.

[0059] The foam may be made, for example, from polyurethane, cellulose,carboxylated butadiene-styrene rubber, polyester foams, hydrophilicepoxy foams or polyacrylate. In a preferred embodiment, the foam isformed from hydrophilic polyurethane foam, such as polyurethane foammade by Reynel Inc. (Boothbay, Me.) under product designation L00562-B.Since the aforesaid foams are hydrophilic per se and further in view ofthe use of the receptacles containing absorbent material, it is notnecessary to treat the foams to render them more hydrophilic in apreferred embodiment.

[0060] In another embodiment, if desired, the foam may be treated so asto be more hydrophilic and therefore increase the tendency of theexudate to coagulate more rapidly in the foam, yet only to the extentthat the foam is not too hydrophilic so that the hydrophilic propertiesof the foam prevents transport of the exudate to the absorbent material.In such an embodiment, the level of hydrophilic properties of theabsorbent foam may be designed such that the surface tension isminimized to allow the easy passage of fluid into foam cells. The fluidis thus retained in the absorbent foam while maintaining a high relativehumidity at the wound site.

[0061] It will be understood that the absorbent core is not limited tobeing constituted of foam. In another embodiment, the absorbent core maybe a porous woven or non-woven material that may be produced by anynumber of means using known materials available to those skilled in theart. For example, the absorbent core may exist as a bulky, looselyformed web composed of very short cellulose fibers arranged in a randomor non-random array, a pad of cellulose flakes, chitosan flakes, or apolymeric fibril matrix.

[0062] The thickness of the absorbent core will range from 0.5 mm to 20mm, and is preferably between 3 mm to 5 mm.

[0063] The absorbent core may include an array of receptacles formedtherein and may be defined in any suitable preselected pattern that cancontain a desired bulk or quantity of discrete portions absorbentmaterial, while maintaining sufficient strength and flexibility suitablefor a dressing of the invention. In a preferred embodiment shown in FIG.1, the pattern of the receptacles 18 is in a grid-like configuration.Preferably, such receptacles have a uniform, predetermined shape andsize, and extend across the distal surface d of the absorbent core. Inthis embodiment, the receptacles are positioned in a rectangularpattern, and the receptacles are generally spaced apart 5 mm (measuredfrom the center axis of each receptacle). The depth of each receptacleis generally 4-5 mm, and positioned at least 0.5 mm from the facinglayer. In this embodiment, the pattern may be tailored to include morereceptacles at specific regions of the dressing as opposed to otherregions.

[0064] In an embodiment of the wound dressing shown in FIG. 11, there isa higher density of receptacles 18 at the central portion 22 of theabsorbent core 14 than near the border portion 24 of the dressing 10.The amount of receptacles at any given region of the absorbent core maybe dependent upon the perceived areas of a greater amount of localoccurrence of fluid, such as at the central portion, to maximize fluidabsorption, and further limit the absorption of fluid at certain areasof the absorbent core such as at the border portion.

[0065] As shown in FIG. 2, the receptacles 18 are arranged to open atthe distal surface of the absorbent core 14 and extend a distance intothe entire thickness thereof. In a preferred embodiment, the receptaclesextend a distance t₁, short of the entire thickness t of the absorbentcore 18, and it is preferred that the receptacles extend a distance70-90% of the total thickness of the absorbent core 14. It will beunderstood, however, that in an embodiment of the wound dressing, thereceptacles may extend through the entire thickness of the absorbentcore.

[0066] In another embodiment of the wound dressing, the receptacles 18may be arranged, as shown in FIG. 13, to extend at different distancesinto the thickness of the absorbent core 14 on the basis of theirlocation and the local occurrence of fluid exuded from a wound site. Inthis embodiment, the receptacles 18 located closer to the center of thedressing 10 extend deeper into the thickness of the absorbent core 14whereas the receptacles 18 closer to the border 24 of the absorbent coreextend a shallower distance into the thickness of the absorbent core 14than the receptacles 18 at the central portion 22. It follows that thedeeper receptacles 18 will contain more absorbent material 20 than theshallower receptacles 18, and therefore provide a greater localizedregion of absorption.

[0067] Since the receptacles preferably extend only partly into thetotal thickness of the absorbent core, exudate will be transported toand absorbed by the absorbent material. This effect leaves the proximalside of the absorbent core without the receptacles in a desirably moistenvironment without excessive saturation of exudate and thus permits thedressing to remain on the wound site for a longer period of time.

[0068] In a preferred embodiment shown in FIGS. 1 and 2, the shape ofthe individual receptacles 18 is uniform and generally cylindrical. Theshape of the receptacles is at least partly chosen to maximize thecontainment of the discrete portions of absorbent material and tofacilitate the migration thereof when swollen by fluid. The receptaclesare not limited to a cylindrical configuration; the receptacles may takeon the shape of pyramids, channels, hemispheres, cones, blocks andtruncated variations and combinations thereof. Moreover, the receptaclesmay include a taper extending from their opening to their base portionso that the receptacles have a greater width near the opening than atthe base portion. This configuration facilitates migration of swollen,moisture-laden discrete portions of absorbent material from thereceptacles so that they can flow more freely from the receptacles.Alternatively, the receptacles may be arranged in a random pattern alonga transverse direction of the distal surface of the dressing.

[0069] In an embodiment of the absorbent core, the receptacles maycomprise a plurality of channels extending transversely along at least aportion of the distal side of the absorbent core. In this embodiment,the channels may have a denticulate or an undulating cross-sectionalprofile. This embodiment may be useful in a wound dressing wherein theabsorbent core is too thin to include receptacles having a form such asthe aforesaid cylindrical receptacles.

[0070] The size of the individual receptacles may be of any suitablesize that will contain a suitable amount of absorbent material that willsufficiently absorb exudate from a wound site. Generally, thereceptacles are sized from about 500 to 5,000 micrometers, preferablyabout 1000-3000 micrometers in cross-section (independently height andwidth dimensions). The receptacles in a preferred pattern have a repeatdistance defined as the distance from one receptacle to the nextreceptacle, center axis to center axis, of 500 to 5,000 micrometers,preferably about 1000-4500 micrometers.

[0071] While in a preferred embodiment the receptacles have a uniformvolume across the transverse directions of the wound dressing, thereceptacles may have varying volumes depending upon the location oftheir openings on the distal surface of the absorbent core. As with theembodiment related to the varying depths of the receptacles, thereceptacles located at or near the central portion of the absorbent coremay have greater volumetric capacity than the receptacles closer to theborder portion of the absorbent core. It follows that the receptacleshaving varying volumes will likewise contain varying bulk amounts ofdiscrete portions of absorbent material.

[0072] The absorbent material used in the dressing of the presentinvention is preferably comprised of superabsorbent polymericgranulates, flakes or powders that swell on exposure to water and form ahydrated gel (hydrogel) by absorbing large amounts of water.Superabsorbents are defined herein as materials that exhibit the abilityto absorb large quantities of liquid, i.e., in excess of 10 to 15 partsof liquid per part thereof. These superabsorbent materials generallyfall into three classes, namely starch graft copolymers, cross-linkedcarboxymethylcellulose derivatives and modified hydrophilicpolyacrylates. Examples of such absorbent polymers are hydrolyzedstarch-acrylonitrile graft copolymer, a neutralized starch-acrylic acidgraft copolymer, a saponified acrylic acid ester-vinyl acetatecopolymer, a hydrolyzed acrylonitrile copolymer or acrylamide copolymer,a modified cross-linked polyvinyl alcohol, a neutralizedself-crosslinking polyacrylic acid, a crosslinked polyacrylate salt,carboxylated cellulose, and a neutralized crosslinked isobutylene-maleicanhydride copolymer. Superabsorbent particulate hydrophilic polymersalso are described in detail in U.S. Pat. No. 4,102,340. That patentdiscloses absorbent materials such as cross-linked polyacrylamides.Preferably, the super absorbent particles used in the dressing of thepresent invention are preferably composed of cross-linkedpolyacrylic-acid.

[0073] Superabsorbent particles are available commercially, for examplestarch graft polyacrylate hydrogel powders are available fromHoechst-Celanese of Portsmouth, Va. Other superabsorbent particles aremarketed under the trademarks SANWET (supplied by Sanyo Kasei KogyoKabushiki Kaisha), SUMIKA GEL (supplied by Sumitomo Kagaku KabushikiKaisha and which is emulsion polymerized and spherical as opposed tosolution polymerized ground particles), and FAVOR (produced by DegussaAG, Dusseldorf, Germany).

[0074] The super absorbent particles are preferably in the form ofgranules or flakes to provide a greater available surface areahydrocolloid. The size of the super absorbent particles is typicallywithin the range of 1 to 1000 micrometers when dry. Preferably, theparticle size range of the absorbent particles is 100 to 900micrometers. The particles which are insoluble in a wound environmenthave an absorptive capacity greater than 0.5 of water per gram of dryparticles.

[0075] In another embodiment, the absorbent material may be ahydrophilic gel that swells upon contact with water. The hydrophilic gelgenerally lacks a cellular or voided internal structure, and is in theform of a solid or semi-solid. Hydrophilic gel may be construed to meanhydrocolloids, hydrogels and combinations thereof as long as thematerial is physiologically tolerable and clinically acceptable. Adescription of suitable hydrophilic gels is provided in U.S. Pat. No.6,566,575 granted to Stickels et al. and such hydrophilic gels arecommercially available.

[0076] In another embodiment of the wound dressing, the absorbent coremay include a plurality of discrete portions of absorbent materialenmeshed in the absorbent core. Such discrete portions of absorbentmaterial may be discrete superabsorbent polymeric granulates, flakes orpowders that are freely disposed in the absorbent core so that they maymigrate within the absorbent core, and preferably towards the distalsurface thereof. In yet another embodiment of the wound dressing, theabsorbent core may include both absorbent material enmeshed therein andthe receptacles containing discrete portions of the absorbent material.

[0077] In summary, in each of the absorbent core embodiments discussedthus far, it is notable that the absorption of the fluid at the portionof the absorbent core near or at its proximal portion is minimized, andthe absorption of fluid is maximized by the absorption of the absorbentmaterial at or beyond the receptacles. Such a mechanism maximizes theamount of fluid that the dressing can absorb, in combination with theconfiguration of the backing layer, and further allows longer wear timefor the patient since the fluid is not in contact with the skin.

[0078] A backing layer may be present in all of the embodiments of thedressing of the present invention. Preferably the backing layer isconformable to animal (inclusive of human) anatomical surfaces, isimpermeable to liquid and is vapor permeable. As discussed above, thebacking layer, in combination with the absorbent core, may beconstructed to define a reservoir therebetween when the dressing is inan expanded moisture-laden state. While the backing layer does notpermit the passage of a liquid or exudate, moisture in the absorbedexudate passes through the backing layer in a vapor form into theatmosphere.

[0079] The preferred embodiment for the backing layer is a thinpolymeric elastic or flexible film coating providing a bacterial barrierformed from a water vapor permeable pliable elastomer material. The filmis continuous in that it has no perforations or pores which extendthrough the thickness of the film. Films of this type are known andgenerally are hydrophilic polymeric materials through which water vaporis capable of diffusing.

[0080] The backing layer is bonded to the proximal surface of theabsorbent core, and in a preferred embodiment, the backing layer isbonded only to the distal surface of the absorbent core and does notpenetrate any pores, cells or cavities therein. Generally, the film is15 to 45 micrometers in thickness, with a preferred thickness of about30 micrometers. The backing layer may comprise polyurethane, such as apolyurethane film available from InteliCoat Technologies (South Hadley,Mass.) under product designation INSPIRE, elastomeric polyester, blendsof polyurethane and polyester, polyvinyl chloride, and polyether-amideblock copolymer. The preferred backing layer for use in the presentinvention is a polyurethane film since it exhibits a resilient propertythat allows the film to have good conformability and further has a highdegree of stretchability.

[0081] It is preferred that the backing layer of the present inventionbe at least translucent, and more preferably, sufficiently transparentso that the wound site to which the dressing is applied can be viewedthrough the dressing. It is advantageous to view to evaluate the woundand healing thereof without removal of the dressing to avoid unnecessaryhandling of the dressing and exposure of the wound to the environment,which reduces the likelihood of contamination.

[0082] Suitable continuous conformable backing layers will have amoisture vapor transmission rate (MVTR) of the backing layer alone of1500 to 14600 g/m{circumflex over ( )}2/24 hrs, preferably 2500 to 2700g/m{circumflex over ( )}2/24 hrs at 38° C. The backing layer thicknessis preferably in the range of 10 to 1000 micrometers, more preferably100 to 500 micrometers. The facing layer of the present invention ispreferably a hydrophobic, liquid and moisture impervious layer bonded tothe proximal surface of the absorbent core. In a preferred embodiment,the facing layer is a cross-linked silicone elastomer gel, such as, forexample, a cross-linked silicone (polydimethyl siloxane gel)manufactured by NuSil Technology (Carpenteria, Calif.) under productdesignation MED-6340. The facing layer preferably has a thickness in therange of 0.05 mm to 0.5 mm, and more preferably 0.1 mm. Theconformability of the dressing to the wound is somewhat dependent onthickness of the components, such that when the dressing is applied to abody portion, it conforms to the surface even when the surface is moved.When the surface is flexed and then returned to an un-flexed position,the facing layer stretches to accommodate the flexation of the joint butis resilient enough to continue to conform to the surface when thesurface is returned to its unflexed condition.

[0083] A silicone facing layer has significant advantages over wounddressings that rely on a glue-type adhesive to secure a dressing to awound. In particular, tacky silicone gels provide a coating which isexceptionally non-adherent to wounds, but which is significantlyadherent to surrounding skin. Moreover, such gels are entirely immobileand unaffected by heat or body exudates. This means that dressingsaccording to the invention retain their non-adherent properties evenafter they have been in place for a substantial period of time, forexample, several days.

[0084] The silicone gel layer adheres gently to surrounding skin sinceit is inherently soft to the touch and flows partly into microscopiccavities and cracks in the skin to create a large contact area over thewound site. As a result, less adhesion force is required to secure thesilicone layer over the wound site than in known dressings that includean adhesive layer having glue. Since the silicone layer more fullydistributes its adhesion force, the peeling strength thereof does notstrip epidermal cells when the dressing is removed from the wound site.Accordingly, the dressing can be reapplied without causing damage to theskin and wound at the wound site. Furthermore, the silicone layerprevents a moisture build-up under such a layer since it is hydrophobicand further since the capillary forces of the absorbent core draw theexudate into the dressing this enables the dressing to be lifted fromthe skin without causing pain to the wearer of the wound dressing.

[0085] The silicones which are used as the facing layer in the dressingof the invention preferably have a Shore A hardness less than 1, andmost preferable have no measurable Shore A hardness.

[0086] When the silicones are formed by cross-linking a mixture of twoor more silicones, the molecular weights of the various components andtheir degree of substitution by reactive groups may be different. Thisallows gels having different physical properties to be formed merely byvarying the proportions of the components.

[0087] The composite facing layer also may include one or more skintreatment agents blended into the silicone elastomer, for examplepetroleum jelly and aloe vera. In a preferred example, up to 20% byweight of the composite elastic layer, preferably 11.9%, may bepetroleum jelly, and up to 3%, preferably 0.1%, may be a secondary skintreatment agent such as aloe vera. It will be understood that differentor additional skin treating agents may be utilized, depending upon theskin condition to be treated by the skin treating agent.

[0088] In a preferred embodiment, the silicone facing layer is formed asa silicone gel sheet having a predetermined pattern of apertures thatare formed prior to the silicone gel sheet being bonded to the absorbentcore. Typically, the apertures will have a diameter of 0.05 to 1.0 mmand there are approximately 50-350 apertures per cm{circumflex over( )}2. While in a preferred embodiment in FIG. 2 the apertures 34 areshown as generally being arranged in a uniform pattern, the facing layer12 is not limited to this arrangement.

[0089] The silicone facing layer may be substantially planar along aproximal surface thereof. Moreover, the silicone facing layer maypenetrate or fill surface irregularities of an absorbent core defined asopenings, crevices or partial pores located along a surface thereof.

[0090] In another embodiment exemplified in FIG. 13, there may be ahigher density of apertures 34 in the facing layer 12 corresponding tothe central portion 22 of the dressing 10 while there is a lower densityor absence of apertures 34 near or along the border portion of thedressing. Alternatively, the facing layer may entirely lack apertures atthe border portion of the dressing, and more particularly, a regioncorresponding to the beveled portion of the absorbent core. This willmitigate fluid absorption at certain areas of the dressing, thereby moreeffectively directing the exudate absorption in areas that will moreefficiently absorb exudate. Furthermore, in yet another embodiment,there is a greater concentration of apertures at or near portions of theabsorbent core having the receptacles to thereby enhance exudate uptaketowards such receptacles.

[0091] Notably, the facing layer is bonded only to the proximal surfaceof the absorbent core and may penetrate the absorbent core a distanceapproximately 50% of its thickness. By forming the apertures prior tobonding to the absorbent core, the facing layer does not occlude thecells nor coat the inside walls of the cells of the absorbent core.Accordingly, suitable permeability of the facing layer is preferablyobtained by providing the facing layer with preformed apertures locatedin a suitable array, and accordingly, there is greater control inestablishing the transit of fluid through the silicone gel layer.

[0092] The thickness of the facing layer may vary across the lengththereof. For example, the facing layer may include regions havinggreater thickness near the border portion of the wound dressing asopposed to the central portion so as to provide greater strength to thefacing layer at such regions thereof having a thicker facing layer.

[0093] In yet another embodiment, the facing layer may include at leasttwo different layers having different properties. For example, a softerlayer to be worn directly adjacent the wound site may be provided thatclosely conforms to the wound site while a harder layer may be providedthat this interposed between the softer layer and the absorbent core toprovide durability and strength to the dressing. The multiple layered ormore aptly dual durometer facing layer adopts the principles describedin U.S. Pat. No. 6,136,039 granted Oct. 24, 2000 owned by assignee ofthe invention described herein, the disclosure of which is incorporatedherein.

[0094] In another embodiment, the facing layer of the present inventionmay comprise a silicone layer of the type mentioned above that isreinforced with an embedded perforated reinforcement layer. Such areinforcement layer may include a non-woven, knitted or woven textilematerial, or a poymeric film such as one made of polyurethane. In thisembodiment, the apertures in the silicone layer generally correspond tothe perforations of the reinforcement layer.

[0095] It will be understood that non-silicone facing layers may beemployed in the dressing of the present invention without departing fromthe scope thereof. Preferably, such facing layers should be soft,flexible, conformable, non-irritating and non-sensitizing. The dressingmay include facing layers that comprise a perforated base filmconstructed of a variety of polymers such as polyurethane, polyethylene,polypropylene, polyamide or polyester material with a pressure-sensitiveadhesive. Furthermore, the facing layer may be in the form of moisturevapor permeable films, perforated films, woven-, non-woven or knit websor scrims. The adhesive may be a microsphere or fibrous adhesive withlow trauma properties and have good adhesion to wet skin. It will beunderstood that the adhesive may be coated on only a portion of thefacing layer, for example, the adhesive may be applied only around theborder portion of the dressing with the central portion lacking anadhesive. Preferably, the facing layer should be perforated so as topermit transport of the fluid therethrough to the absorbent core.

[0096] The dressing the present invention can include variouscombinations of ingredients without departing from the scope of thepresent invention, including, for example, medicaments, soaps,disinfecting and sterilizing agents, odor management, hemostatic agents,proteins, enzymes and nucleic acids. Preferably these agents may beincorporated directly or dispersed in the absorbent core, or dispersedwith the absorbent material. Alternatively, these ingredients may beincorporated into the dressing by any suitable means, including anadditional layer to the absorbent core that would incorporate suchingredients.

[0097] Suitable medicaments, soaps, disinfecting and sterilizing agents,proteins, and enzymes are commercially available. Preferably suchmedicaments may include antifungal agents, antibacterial agents,angiogenesis promoting agents and other appropriate agents.

[0098] As mentioned above in observing FIG. 10, the facing layer 12 mayinclude an adhesive that is provided near or at a peripheral borderportion of the facing layer. Preferably, this adhesive is a pressuresensitive silicone such as an adhesive silicone manufactured by NuSilTechnology (Carpenteria, Calif.) under product designation MED-1356 or avery tacky silicone manufactured by NuSil Technology (Carpenteria,Calif.) under product designation MED-6345. The adhesive silicone mayapplied to a silicone facing layer after the facing layer is cured suchthat the adhesive silicone is applied to the facing layer when it is ina partially cured state and then finishes curing when on the facinglayer. Alternatively, the adhesive may be an acrylate glue or hot meltglue applied onto the facing layer using conventional methods forapplying an adhesive to a substrate.

[0099] In a preferred method of the invention, the tacky silicone gel isprepared from a two-component silicone, such as MED-6340 parts A and Bproduced by NuSil Technology (Carpenteria, Calif.). The two parts A andB each include the same base, vinyl-substituted, poly(dimethlysiloxane).In addition, part A includes a platinum catalyst to facilitate areaction between parts A and B when they are mixed. Part B includes across-link, hydride-containing silicone. Both parts A and B are easilymixed, and handled separately, do not react or cure.

[0100] The tacky silicone gel is produced by thoroughly mixing parts Aand B in a ratio of 1:1, thereby enabling the vinyl-group on thevinyl-substituted silicone to be activated by the catalyst and thehydride containing silicone. This results in cross-linking the siliconeso that it will begin to cure. One of the factors that influences thetime required for curing is the temperature of the mixed combination ofparts A and B. A suitable temperature range is 50-150° C., preferably100-130° C. Another factor that influences the curing time is the amountof catalyst that is used in the combination of parts A and B, howeverthe catalyst may also undesirably influence the tackiness of thesilicone gel. Typically, in the present invention, the curing time of a0.1 mm thick silicone gel facing layer cured at 100° C. is approximately1 minute, and the silicone gel facing layer is normally transferred tothe absorbent core when it is in a partially cured state in a range of3-12 seconds after parts A and B have been mixed.

[0101] It will be understood that the aforementioned steps for preparingthe tacky silicone gel are provided for exemplary purposes and theinvention is not meant to be limited by such steps. Any suitable stepsfor preparing a partially cured tacky facing layer may be used whilestill being within the scope of the present invention.

[0102] In the context of the present invention, “partially cured”silicone denotes that the silicone is not completely cured and thereforethe silicone is not fully cross-linked. Typically, the parameters foryielding a partially cured silicone layer must be establishedempirically with respect to the gel mixture and absorbent material used.While the parameters for yielding a “partially cured” silicone layer mayvary, the ratio of time required for the silicone gel to become fullycured may be employed to determine if the silicone layer is partiallycured. Specifically, in the present invention, the silicone layer ispartially cured between 5-70% of the total time required to cure thesilicone gel. It follows that the time interval to apply the facinglayer to the absorbent core is between 5-40%, or more preferably 5-20%.

[0103] When curing the silicone layer, a catalyzer may be used to speedup the curing time and reduce the tackiness of the silicone gel. Asilicone catalyzer is commercially available from NuSil Technology(Carpenteria, Calif.) under the product designation CAT-50.

[0104] Another preferable feature of the facing layer of the presentinvention is a variable tackiness across the surface thereof. Accordingto this feature, the tackiness of the facing layer is configureddifferently at different regions thereof. For example, regions of thefacing layer near or at the border portion of may be provided with agreater tackiness than the central portion of the facing layer. Thetackiness may be disposed in a gradient across a half section of thefacing layer from a maximum at or near the border portion of the facinglayer to a minimum at or near the central portion of the facing layer.An embodiment of the wound dressing having a facing layer 12 withvariable tackiness is exemplified in FIG. 14. As shown, the facing layer12 may be provided in discrete multiple sections having generallyuniform tackiness such as a border portion 33 having greater tackinessthan a central portion 37 and an intermediate portion 35 of the facinglayer 12. The tackiness may gradually increase from the central portion37 towards the border portion 33, or the tackiness may remain relativelyconstant in each discrete portion 33, 35, 37.

[0105] The facing layer is not limited to a border portion having auniform tackiness. The facing layer may include at least one side of theborder portion having tackiness greater than other portions thereof. Forexample, as exemplified in FIG. 15, if the dressing has a generallysquare or rectangular configuration, two opposing sides 39 correspondingto the border portion of the facing layer 12 may have a greatertackiness than the remaining opposing sides 41 of the facing layer.Alternatively, in the event the dressing has a generally circularconfiguration or variations thereof, as shown in FIG. 16, sections 43 ofthe facing layer 12 corresponding to the border portion thereof may havea greater tackiness than other sections of the border portion of thefacing layer 12.

[0106] According to a 90° peel-off test from a stainless steel surface,the tackiness corresponding to the central portion of the siliconefacing layer is generally within the range of 0.05 N-1.0 N andpreferably within the range of 0.1 N to 0.4 N. The tackinesscorresponding to the border portion of the silicone facing layer iswithin the range of 0.5 N-5.0 N and preferably within the range of 0.8N-3.0 N.

[0107] The facing layer with variable tackiness may be obtained byforming a facing layer wherein areas thereof have different mixtures ofsilicone components, the presence or different quantities of siliconecatalyzer or other components, exposure to different curing conditionssuch as pressure or temperature, or any other method known to oneskilled in the art of obtaining different tackiness in a siliconesubstrate. Moreover, in the embodiments such as those exemplified inFIGS. 14-16, discontinuous discrete sections of the facing layer havingdifferent tackiness can be prepared and applied to the absorbent coreseparately or the facing layer can be formed with a continuous facinglayer having discrete sections of different tackiness.

[0108] In another embodiment of the wound dressing exemplified in FIG.17, the backing layer 16 may be configured so as to define a bordersection 45 that extends beyond the border of the absorbent core 14 andthe facing layer 12 disposed thereon. The border section 45 of thebacking layer 16 preferably surrounds the peripheral edges of theabsorbent core 14 and the facing layer 12. The border section 45 of thebacking layer 16 may be provided with a skin adherent adhesive or anelastomeric gel that is preferably tackier than the facing layer 12. Thestronger adhesion of the border section 45 of the backing layer 16permits the dressing 10 to remain firmly in place over a wound site. Inthis embodiment, the facing layer 12 preferably has a gentle adhesionthat will prevent traumatization of a wound upon removal therefrom.

[0109] In yet another embodiment shown in FIG. 18, the backing layer 16is adhered to the absorbent core 14 such that the absorbent core extendsfrom the backing layer 16. The facing layer 12 is configured to extendaround the sides of the absorbent core 14 and will generally extend tomeet with the backing layer 16. The backing layer 16 includes a bordersection 45 that may have a stronger tackiness than the facing layer 12.

[0110] In the embodiments shown in FIGS. 17 and 18, the backing layermay be provided with or without the aforementioned compliant element andthe absorbent core may be provided with or without the receptaclescontaining discrete portions of absorbent material.

[0111] The entirety of the side of the backing layer adjacent theabsorbent core may include the skin adherent adhesive or an elastomericgel used for the border section 45. In a such an embodiment, the skinadherent adhesive or an elastomeric gel, however, is preferably disposedon the backing layer so that it does not prevent moisture transfertherethrough. In the alternative, the skin adherent adhesive or anelastomeric gel disposed on the border section of the backing layer maybe applied, such as sprayed or spreaded, to the border section of thebacking layer after the backing layer is applied to the absorbent core.

[0112] The method of manufacturing this embodiment may be conductedusing one of the methods described herein for applying the backing layerto the absorbent core. Alternatively, one side of the backing layer maybe coated with a discontinuous adhesive or elastomeric gel on a sidethat will face the absorbent core. The backing layer is thus placed ontothe absorbent core so that the backing layer extends over an entiresurface thereof wherein a section of the backing layer extends beyondthe peripheral edges of the absorbent core to define the border section.Prior to applying the backing layer to the absorbent core, a primer maybe applied to the side of the absorbent core adjacent to the backinglayer such that the primer is applied discontinuously so that the primerdoes not prevent transport of moisture through the backing layer whenapplied on the absorbent core.

[0113] In a preferred method, the facing layer and its apertures areformed prior to being bonded onto the absorbent core. A perforationdevice 42 is preferably used to form the facing layer and its apertures.As shown in FIGS. 19 and 20, the perforation device 42 includes agenerally planar carrier surface 47 having a plurality of needle-likeperforating elements 44 that extend a distance therefrom. Theperforation device 42, including the carrier surface 43 and theperforating elements 44, is selectively heated to a curing temperatureof the silicone. The carrier surface 47 and the perforating elements 44are coated with a release film, such as TEFLON.

[0114] In a preferred embodiment, the perforating elements extend adistance slightly greater than the thickness of the silicone layer, andcan vary in length from 0.02 to 1.0 mm with a preferable length of0.1-0.2 mm. While in this embodiment the perforating elements have agenerally circular cross-section, the pins are not limited to thisconfiguration. For instance, the pins may alternatively have across-section configured in a triangular, square, rectangular or anyother suitable shape or combination thereof. The perforation device hasa density of 5 to 300 perforating elements per cm{circumflex over ( )}2,and preferably there are 100 perforating elements per cm{circumflex over( )}2.

[0115] When forming the facing layer, a discrete layer of uncuredsilicone gel is disposed on the carrier surface of the perforationdevice such that the perforation elements extend through the layer ofsilicone gel. The uncured silicone layer generally has a thicknessranging between 0.05-0.5 mm. The perforation device is heated to apredetermined temperature, about 100° C. or to any other suitable curingtemperature of the silicone gel, either before or after the silicone gelis placed thereon. The silicone gel will begin to cure along an innerside portion thereof that is adjacent to the carrier surface as it issmoothed over the carrier surface. It will be understood, however, thatit is not desirable that an outer side portion of the silicone gel thatis opposed to the inner side portion of the silicone gel fully cure.This is so that the outer side portion will have sufficient tackiness toadhere to the absorbent core when pressed thereagainst and will thusenable the silicone gel to finish curing while disposed on the absorbentcore itself.

[0116] The absorbent core is placed on the side of the facing layer thatis opposite the side adjacent the carrier surface. Since the siliconegel is in a partially cured state, the silicone gel will cure and adhereto the surface of the absorbent core. When the silicone gel has fullycured, the silicone layer is removed from the perforation device alongwith the absorbent core. Pressure may be exerted onto the absorbent coreand the facing layer to more fully adhere the facing layer to theabsorbent core.

[0117] The silicone layer may be removed from the perforation deviceprior to be being applied to an absorbent core. In this instance, thesilicone layer may be peeled away from the perforation device when it isin a partially cured state, thus forming a discrete, partially curedsilicone layer that can be applied to a transfer film or substrate forfuture application to an absorbent core or directly to a body member.The transfer film may be an air permeable paper or similar type of filmor paper that will easily permit the silicone layer to be applied andremoved therefrom when substantially or fully cured.

[0118] The perforation device may be modified in view of the descriptionprovided above. Specifically, the carrier surface of the perforationdevice may include a plurality of holes extending therethrough wherein aplurality of discrete perforation elements is slidably disposed throughthe plurality of holes. The method for using this perforation deviceincludes the steps of heating the planar surface and perforatingelements of the perforation device, and placing a layer of uncuredsilicone gel on the planar surface of the perforation device. Oncedisposed upon the planar surface, the perforation elements are driventhrough the silicone layer. After the silicone layer is at leastpartially cured, the perforation elements are withdrawn from thesilicone gel layer. An absorbent core may then be applied onto thesilicone layer as the silicone layer cures. Alternatively, the siliconelayer may be left to fully cure on the perforation device and thensubsequently removed, or the silicone layer may be removed prior tofully curing.

[0119] In another method for applying the facing layer to the absorbentcore in the present invention, a partially cured, silicone layer 12 isdeposited onto a transfer film upon which apertures are formed in thesilicone layer 12 by rotating a mechanical roller 46 thereon. Asexemplified in FIG. 21, the mechanical roller 46 has a patterned surfacethat is similar in construction to the carrier surface 43 and theperforation elements 44 of the aforesaid perforation device 42 depictedin FIGS. 19-20. In forming the apertures, perforation elements 44 of themechanical roller 46 are heated to about 100° C. or to the curingtemperature of the silicone layer. The mechanical roller 46 may eitherbe applied against the partially cured silicone layer after the siliconelayer 12 has been applied to the absorbent core 14 or may be appliedagainst the silicone layer while adhered to a transfer film prior to theapplication thereof to the absorbent core.

[0120] The mechanical roller may include the slidable perforatingelements, as described in reference to an embodiment of the perforatingdevice and function generally in the same way.

[0121] In another method, uncured silicone gel may be extruded directlyonto a heated mechanical roller, similar to the type described above,rotating at a predetermined speed. A length of the absorbent corematerial is supported by a conveying surface and positioned below themechanical roller. As the mechanical roller rotates, the partially curedsilicone gel is deposited onto the absorbent core material by therotating mechanical roller which applies at least a slight pressure onthe absorbent core. The mechanical roller is configured and arranged torotate at a sufficient speed so that the silicone gel will be nearly orfully cured as it leaves the carrier surface and is applied to theabsorbent core.

[0122] A silicone primer, such as a silicone primer manufactured byNuSil Technology (Carpenteria, Calif.) under product designationCF6-135, may be used to facilitate the bonding of the silicone layer tothe absorbent core.

[0123] In yet another method for applying a facing layer to an absorbentcore, as exemplified in FIG. 22, a partially cured, non-perforatedsilicone layer 12 may be applied to a transfer film 38. The film 38carrying the silicone layer 12 is then reversed in orientation so thatthe film 38 defines an upper surface and the silicone layer 12 defines alower surface. The silicone layer 12 is then slowly positioned on anupper surface of the absorbent core 14. After the silicone layer 12 isgently pressed onto the absorbent core 14, a perforation device 42carrying a plurality of perforating elements 44 having a similarconstruction to the aforementioned perforation device 42 depicted inFIGS. 19 and 20 is positioned over a lower surface of the absorbent core14. This perforation device 42, however, is distinct from theperforation device of FIGS. 19 and 20 in that each of the perforatingelements 44 includes a discrete air passageway and may generally belarger therefrom.

[0124] The perforating elements 44 are inserted into at least a portionof the thickness of the absorbent core 14 and air is blown through theneedles 44 towards respective portions of the silicone layer 12. The airblown through the perforating elements 44 cures the silicone layer 12and further forms apertures through the silicone layer 12. After anadequate period of time and upon formation of the apertures, the device42 carrying the needles 44 is withdrawn from the absorbent core 14. Thefilm 38 is subsequently removed from the silicone layer 12. A siliconeprimer, as described above, may be applied to the absorbent core 14 tothe application of the silicone layer 12 thereon to improve theadherence of the silicone layer to the absorbent core.

[0125] In yet another method exemplified in FIGS. 23 and 24 for applyingthe facing layer 12 to the absorbent core 14, a patterned negativesurface 48 is provided that bears the negative impression of theeventual silicone layer 12. The patterned surface 48 includes a seriesof peaks and valleys 50, 52 that correspond to the eventual pattern ofapertures of the silicone layer 12. A partially-cured silicone gel 54 isapplied to the patterned surface 48 whereupon the silicone gel 54 restsin the valleys 52 while at least a top portion of the peaks 50 extendtherethrough. The absorbent core 14 is subsequently positioned over thesilicone gel 54 with the top portion of the peaks 50 penetrating theabsorbent core 14. The silicone gel 54 is then bonded to the absorbentcore 14 and the patterned surface 48 is removed from the thus formedsilicone layer 12. Removal of the patterned surface 48 imparts apredetermined pattern of apertures on the silicone layer 12 thatcorrespond to the peaks 50 of the patterned surface 48.

[0126] In yet another method for applying a facing layer to an absorbentcore, a silicone gel is mostly cured in a container. At a moment inwhich the silicone gel has reached a suitably thick consistency, thesilicone is sprayed onto the absorbent core in a systematic manner so asto adhere thereto. While the silicone is sprayed onto the absorbentcore, a plurality of apertures is formed along the silicone layer. Thespraying of the silicone is conducted in a controlled manner thatpermits the holes to be formed in a non-random, predetermined pattern.The silicone layer may be sprayed onto the absorbent core so as toinclude an undulating surface.

[0127] In each of the aforesaid methods for applying a facing layer ontoan absorbent core, it is essential that the silicone does not coat thewalls of the cells or pores of the absorbent core. The objective is notto occlude the cells or pores with silicone and provide uninhibitedfluid transport from the facing layer to the absorbent layer.Furthermore, it is preferred that the holes formed through the siliconefacing layer of the invention be arranged in a predetermined pattern soas to provide greater control of the fluid that passes through thesilicone facing layer when the dressing of the invention is applied to awound site.

[0128] In any of the foregoing methods, the facing layer and theabsorbent core are adhered to each other substantially uniformly alongtheir opposed areas. Furthermore, in each of the foregoing methods, theapertures of the facing layer may be formed either before or after thefacing layer is applied to the absorbent core. The perforating elementsor peaks may or may not extend a distance into the absorbent core if theabsorbent core is applied to the facing layer while the facing layer ispositioned on a perforation device. It will be understood, that it ispreferred that the facing layer be partially cured when applied to theabsorbent core so as to be sufficiently tacky to adhere to the absorbentcore, yet substantially cured so that additional apertures are notformed therethrough by capillary action of the cells or pores of theabsorbent core.

[0129] In a method exemplified in FIGS. 25-28, the preparation of theabsorbent core 14 of the dressing 20 of the invention may be conductedas follows. First, a plurality of projection elements 56 are heated to asuitable temperature and are inserted into a surface of the absorbentcore 14. The projection elements 56 are heated to a temperature in therange of 200-300° C., preferably 255° C. The projection elements 56extend into the absorbent core 14 a distance less than its totalthickness. The projection elements 56 are preferably arranged in apattern bearing the negative impression of the receptacles 18 of theabsorbent core 14. The projection elements 56 are removed from theabsorbent core 14 after a period of time, thereby forming thereceptacles 18 in the absorbent core 14.

[0130] The discrete portions of absorbent material 20 are deposited intothe receptacles 18 by positioning a silicone film 58 between aligned topand bottom plates 60, 62 having a plurality of holes 64 corresponding tothe plurality of projection elements 56 used to form the receptacles 18.A predetermined amount of the absorbent material 20 is deposited intoeach of the holes of the top plate 60 and the projection elements 56used to form the receptacles are inserted through the plurality of holesof the top and bottom plates 60, 62, and the silicone film 58 so as todeposit and compact the absorbent material 20 into each of thereceptacles 18.

[0131] While the bulk amount of absorbent material in each receptaclemay be varied, it is preferred that the amount of absorbent materialshould not fill the entire receptacle since wetted absorbent materialwill swell. It will also be understood that it is important to themethod that the portions of the absorbent material not be compacted inthe receptacles to the degree that migration of such absorbent materialis obstructed.

[0132] It will be understood that the present invention is not limitedto the aforementioned method for depositing the absorbent material inthe receptacles. Any method that may permit insertion and compaction ofdiscrete portions of absorbent material in the receptacles in acontrolled fashion may be employed while still remaining within thescope of the invention.

[0133] For example, a simple approach for depositing absorbent materialin the receptacles, in the event that superabsorbent granulates orpowders are used, comprises the step of depositing the absorbentmaterial into each of the receptacles and then brushing, blowing orwiping off excess absorbent material from the surface of the absorbentcore. A vibration table or similar vibration mechanism may be used tourge the absorbent material to settle in the receptacles.

[0134] In the aforementioned method, it will be understood that thefacing layer and the absorbent core are at least adhered and sealed toeach other at the border portions thereof. The importance of this isthat the facing layer must be secured to the absorbent core so that thediscrete portions of absorbent material do not leak from the wounddressing.

[0135] A method for securing the backing layer 16 to the absorbent core14 and formation of the compliant element 26 is preferably performed asillustrated in FIGS. 29-34. In a preferred method, a platen 66, as shownin FIG. 29, may be provided and configured with a profiled surface 70corresponding to the compliant element 26 and the central 22,intermediate 23 and border portions 24 of a dressing of an embodiment ofa wound dressing of the invention. The platen 66 is selectively incommunication with a vacuum configured to draw a vacuum along itsprofiled surface 70 and is heated to a temperature in the range of150-200° C., preferably 185° C. In a preferred embodiment, the platen 66includes a groove 68 that extends around the profiled surface 70 thatdefines the form of the compliant element 26. The platen 66 includes atleast one passageway 72 in communication with the groove 68 and avacuum. The platen 66 may also include a knife edge 74 that extendsaround the peripheral edge of the profiled surface 72 and a beveledportion 76 near the peripheral edge.

[0136] The platen 66 includes at least one recessed portion, such asrecessed portions 78, 80, 82 and 84 shown in FIG. 29, that may bedisposed about a central portion of the platen 66. The recessed portions78, 80, 82 and 84 are preferably defined in a step-wise configurationwith the central recessed portion 84 being relatively deeper than afirst recessed portion 78. The at least one recessed portion is providedto reduce the pressure exerted at the localized region of thecorresponding absorbent core. This results, at least in part, indecreasing the level of adherence of the backing layer at such localizedregion to the absorbent core. It will be noted that the platen is notlimited having recessed portions only in a central portion thereof andmay be provided along any portion of the platen where it is desired tohave a localized region of less adherence of a backing layer to anabsorbent core.

[0137] The platen 66 may include a plurality of such passageways 72 thatare utilized to communicate the vacuum with a backing layer 16. Forexample, the platen 66 may include 8 equally spaced passageways aboutthe groove 68 when an absorbent core has a generally rectangular shape.In this example, a passageway may be provided at a locationcorresponding to intermediate portion of the absorbent core and apassageway may be provided between each corner. Moreover, the platen mayinclude at least one additional passageway 73 that is in communicationwith compressed air, and such at least one additional passageway may bedisposed on the platen corresponding to either the central or borderportions.

[0138] It will be noted that the platen may be configured according tothe shape of the eventual wound dressing and its individual features.For example, the platen may be arranged in a generally circular shapehaving a groove that is generally circular.

[0139] As shown in FIG. 30, the backing layer 16 is placed over theabsorbent core 14, and then, as shown in FIG. 31, the platen 66 ispositioned against the backing layer 16 and draws the backing layer 16towards its profiled surface 70 by the vacuum. The platen 66 iscontinually drawn towards the absorbent core 14 while drawing thebacking layer 16 against its profiled surface 70. Of note is that aportion of the backing layer 16 is preferably drawn into the groove 68,thereby forming at least a portion of the compliant element 26. In FIG.31, the platen 66 is heated at portions of the profiled surface 70corresponding to the central, intermediate and border portions 22, 23,24 of the eventual dressing. The surface of the groove 68 may or may notbe heated.

[0140] In FIG. 32, the platen 66 positions the backing layer 16 againstthe absorbent core 14. As can be seen in FIG. 33, the knife portion 74effectively cuts the absorbent core 14 and backing layer 16, and impartsthe beveled portion 28 of the border portion 24 to the dressing 10.Prior to withdrawing the platen 66 from the absorbent core 14, as shownin FIG. 33, the vacuum is removed from the profiled surface 72 and airprojected against the backing layer generally at the central portionthereof. As illustrated in FIG. 34, the platen 66 is subsequentlyremoved from the formed absorbent core 14 with the backing layer 16.

[0141] In another embodiment, the profiled surface of the platen may beconfigured so that a central portion thereof corresponding to thecentral portion of the dressing extends so that it imparts a thicknessto the absorbent core that is less than at the area corresponding to thecompliant layer and the border portion. This is so that the backinglayer will adhere more loosely to the absorbent core at the centralportion of the wound dressing. Due to the difference in thickness of theabsorbent core, the dressing will have the benefit that the discreteportions of absorbent material will cause the backing layer to detachfrom the absorbent core more effectively, and will further prevent thebacking layer from detaching from the border portion of the dressingbefore detaching at the central portion of the dressing.

[0142] It will be understood that the above described embodiments of theinvention may assume a variety of different shapes, sizes andconfigurations without departing from the scope of the presentinvention.

[0143] It will be understood that the above described embodiments of theinvention are illustrative in nature, and that modifications thereof mayoccur to those skilled in the art. Accordingly, this invention is not tobe regarded as limited to the embodiments disclosed herein, but is to belimited only as defined in the appended claims.

We claim:
 1. A wound dressing comprising: an absorbent core havingopposed proximal and distal surfaces including central and borderportions; a discrete skin adherent, elastomeric gel facing layer havinga distal surface secured to the proximal surface of the absorbent core,said facing layer having a plurality of through extending aperturesarranged in a pattern; and a discrete pressure sensitive adhesive layerapplied to the facing layer on at least a segment of a proximal surfacethereof.
 2. The wound dressing according to claim 1, wherein theplurality of apertures of the facing layer are generally located along acentral portion thereof corresponding to the central portion of theabsorbent core.
 3. The wound dressing according to claim 2, wherein aborder portion of the facing layer generally corresponding to the borderportion of the absorbent core is substantially free of said apertures.4. The wound dressing according to claim 1, wherein the adhesive layeris located along at least one segment of a border portion of the facinglayer corresponding to the border portion of the absorbent core.
 5. Thewound dressing according to claim 4, wherein the adhesive layer isapplied to at least two opposed sides of the border portion of thefacing layer.
 6. The wound dressing according to claim 1, wherein theadhesive layer has greater skin adherence properties than theelastomeric gel of the facing layer.
 7. The wound dressing according toclaim 1, wherein the adhesive layer is only applied near the peripheralborder of the facing layer.
 8. The wound dressing according to claim 1,wherein the apertures of the facing layer are provided only at a centralportion of the facing layer corresponding to a central portion of theabsorbent core, said adhesive layer is applied in a region bordering thecentral portion of the facing layer.
 9. The wound dressing according toclaim 1, wherein the adhesive layer is generally apertured.
 10. Thewound dressing according to claim 1, wherein the adhesive layer is anacrylate glue.
 11. The wound dressing according to claim 1, wherein theadhesive layer is a silicone gel sprayed onto the facing layer.
 12. Awound dressing consisting: a discrete skin adherent, elastomeric gelfacing layer having distal and proximal surfaces, said facing layerhaving a plurality of through extending apertures arranged in a pattern;and a discrete pressure sensitive adhesive layer applied to the facinglayer on at least a segment of a proximal surface thereof.
 13. The wounddressing according to claim 12, wherein the adhesive layer is locatedalong at least one segment of a border portion of the facing layer. 14.The wound dressing according to claim 13, wherein the adhesive layer isapplied to at least two opposed sides of the border portion of thefacing layer.
 15. The wound dressing according to claim 12, wherein theadhesive layer has greater skin adherence properties than theelastomeric gel of the facing layer.
 16. The wound dressing according toclaim 12, wherein the adhesive layer is only applied around a peripheralborder of the facing layer.
 17. The wound dressing according to claim12, wherein the apertures of the facing layer are provided only at acentral portion of the facing layer, said adhesive layer is applied in aregion bordering the central portion of the facing layer.
 18. The wounddressing according to claim 12, wherein the adhesive layer is generallyapertured.
 19. The wound dressing according to claim 12, wherein theproximal surface of the facing layer is generally planar.
 20. The wounddressing according to claim 12, wherein the distal surface of the facinglayer is generally planar.